# Wind of presupernova IIn SN~1997eg

## TL;DR

This study analyzes spectra and photometry of supernova SN 1997eg to determine the properties of its circumstellar wind, revealing a lower wind velocity and a high mass loss rate, indicating a red supergiant progenitor.

## Contribution

The paper provides a revised measurement of the presupernova wind velocity and mass loss rate, challenging previous assumptions and offering new insights into the progenitor's nature.

## Key findings

- Wind velocity is 20 km/s, lower than previously thought.
- Mass loss rate is approximately 1.6 x 10^{-3} solar masses per year.
- Progenitor was a massive red supergiant, not an LBV-supergiant.

## Abstract

Spectra and phototometry of type IIn supernova SN 1997eg are used to determine properties of the circumstellar gas lost by the presupernova during the latest 200 years before the explosion. The analysis of narrow H$\alpha$ and [Fe X] 6374 \AA\ results in the wind velocity $u = 20$ km/s, significantly lower than the earlier accepted value (160 km/s) upon the bases of the radial velocity of a blue absorption wing of the narrow H$\alpha$. That high velocity of the wind in our picture is related to the preshock gas accelerated by the cosmic ray precursor. The modelling of the circumstellar interaction results in the wind density parameter $\dot{M}/u$ that being combined with the wind velocity suggests the presupernova mass loss rate of $1.6\cdot10^{-3} M_{\odot}$ yr$^{-1}$. The wind density is consistent with the [Fe X] 6374 \AA\ luminosity. The model H$\alpha$ luminosity also agrees with the observational value. Recovered wind properties indicate that the presupernova at the final evolutionary stage was a massive red supergiant with a high mass loss rate, but not the LBV-supergiant as suggested earlier.